CET Quarterly News ISSUE 20 JUNE 2012 Chemical Characteristics, Geodynamic Settings, and Petrogenesis of Gold-Ore-Forming Arc Magmas Robert Loucks1 Introduction This article examines the linkage between variations of geodynamic setting at convergent plate margins and variations of magma chemistry in gold-ore-productive arc segments and epochs, as compared to gold-unproductive ordinary arc magmatism in intra-oceanic arcs and continental- margin magmatic belts. Low- to high-potassium tholeiitic and calc-alkalic arc magmas that exsolve a gold-ore-forming magmatic-hydrothermal fluid at some stage of crystallisation are distinguished from ordinary tholeiitic and calc-alkalic arc magmas by higher contents of lithophile elements that partition strongly into melt relative to residues during partial melting of mantle peridotite. The pattern of element enrichments that distinguishes gold-productive from gold-infertile arc magmas mirrors the chemical distinction between sub-arc lithospheric mantle and asthenospheric upper mantle. Gold-ore-productive arc segments occur where the geodynamic setting is conducive to exceptional participation of lithospheric mantle in the melting column. continued on page 4. 1 Adjunct Senior Research Fellow, Centre for Exploration Targeting, University of Western Australia, [email protected] In this issue... 14 Student Success in CET Magmatic Mineral Systems theme 16 CET hosts acclaimed academic Figure 1. Locations of Plio-Pleistocene (P) and latest Miocene (M) intrusive-related gold deposits containing >10 tonnes of gold (yellow dots) and porphyry copper-gold deposits (orange dots) in the northwestern Pacific, shown with respect to the distribution of 26 Valuing Vendor Consideration: trenches, aseismic ridges and oceanic plateaus, fossil and active back-arc spreading Performance shares & options centres, and plate convergence vectors. Deposit ages (Ma) are shown. Photo (top): An exploration drill rig on Lake Lefroy, south of Kambalda. This photograph is reproduced with the kind permission of BHP Billiton Mineral Exploration, from the Western Mining Corporation Holdings Limited 1990 Annual Report to Shareholders. CET NEWSLETTER ISSUE 20 JUNE 2012 Corporate Membership 2012 MAJOR PRODUCER Anglo American Exploration Pty Ltd First Quantum Minerals Australia Ltd Norilsk Nickel Australia AngloGold Ashanti Australia Ltd Gold Fields Australasia Pty Ltd Paladin Energy Barrick Gold of Australia Ltd Iluka Resources Ltd Rio Tinto Exploration Pty Ltd BHP Billiton Ltd MMG Exploration Pty Ltd Teck Australia Pty Ltd Cameco Australia Pty Ltd Newcrest Mining Ltd De Beers Canada Exploration Newmont Mining Services Pty Ltd EMERGING PRODUCER Alacer Gold Corp Focus Minerals Ltd Sinosteel Midwest Corp Ltd Alkane Resources Ltd Heron Resources Ltd St Barbara Ltd Atlas Iron Independence Group NL Teranga Gold Birla Maroochydore Pty Ltd Integra Mining Ltd Troy Resources NL Cliffs Natural Resources Pty Ltd Mincor Resources NL Kingsgate Consolidated PMI Gold Corporation JUNIOR EXPLORER Anglo Australian Resources NL Enterprise Metals Ltd Musgrave Minerals Ltd Aurora Minerals Ltd Gold Road Resources Nero Projects Australia Ausgold Ltd Hampton Hill Mining NL Newexco Services Pty Ltd Breakaway Resources Ltd Image Resources NL Pioneer Resources Ltd Brockman Resources Ltd La Mancha Resources Australia Regalpoint Exploration Pty Ltd CIA. 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Creasy Tanami Gold NL Encounter Resources Ltd Mitchell River Group Trafford Resources Ltd IN KIND Datamine Gemcom Australia Pty Ltd Micromine Pty Ltd Digirock Pty Ltd Geosoft Australia Pty Ltd Runge Ltd Earth Mapping Resourcing Ltd ioGlobal Zaparo Ltd (Leapfrog) Equinox Minerals Ltd Maptek Pty Ltd New Corporate Members Corporate Members have access to a Members ONLY exploration, Corporate Members will have the first secure site, www.cetmembers.com opportunity to participate, At this site Corporate Members have EXCLUSIVE access – Get prominent recognition on the CET web site, in CET to: Annual Report, on the University of Western Australia – Copies of presentations and pre-publication release of campus, and when CET attends international and research outcomes, national conferences, seminars, lectures and other public events. – Quarterly CET Newsletters, and – Get preferred access to CET research staff and – Early access to non-proprietary research outcomes and distinguished visiting researchers, ideas in a user-friendly format. – Opportunities to network with students, your future Corporate Members also: employees, through seminar series and networking – Receive a 30% discount on CET delivered Training functions for Members, and Courses and 20% discount on externally delivered – Get the use of the CET logo. courses, For more information on how to become a Corporate – Become a preferred research partner; as CET staff Member please visit our website www.cet.edu.au or develop new concepts and tools to apply to mineral phone +61 8 6488 2636. 2 From the Director growth come challenges. We summarise with an outlook on some of these challenges and the exciting directions CET is heading. The annual review also refers readers to our recently revamped CET website, where the global reach of our research initiatives can be viewed, and details on key research projects, training initiatives and CET team members can be found (www.cet.edu.au). In summary, on behalf of the staff and students of CET I would like to thank all stakeholders for their continued engagement with and support of CET, which has been critical to our success. I invite all of you to continue to engage with us, helping to shape our centre’s research directions into the future and becoming part of the excitement. I look forward to meeting with you at the various CET, industry and As the CET’s 7th anniversary approaches, I am happy academic forums during the coming year. to report that your Centre for Exploration Targeting is performing very well on all fronts, including record industry engagement (75 members), record turnover (projected as $7M in 2012), record staff and student numbers (45 staff and 30 PhD’s), and academic output not only to industry training courses and T. Campbell McCuaig industry journals, but to the highest academic CET Director levels (e.g. Nature and Nature Geoscience). One of the key ways we communicate CET’s activities and research outcomes to you is in the form of this newsletter. I believe the CET Newsletter is one of the best of its kind, and we continually get favourable reviews of the breadth and depth of information reported in it from both industry and academic stakeholders. Yet with the tremendous growth of CET’s research activity and outputs, it is difficult to give anything more than a snapshot of the exciting work CET is undertaking in these newsletters. To facilitate communication of how CET is tracking, we have instigated an annual review that will be issued with the CET’s June Newsletters, the first of which accompanies this issue. An impressive sixty-eight West Australian academics and industry members attended The purpose of this annual review is to provide the Australian Academy of Science’s Exposure all CET stakeholders in academia, industry and Draft workshop at the University of Western government with a snapshot of the centre at the Australia to contribute to the future direction of end of the previous calendar year, and a glimpse geoscience. of what CET is set to achieve in the near future. Our chairman, Dr. Jon Hronsky, also provides a CET representatives provided feedback on statement to stakeholders to give an independent the “Searching the Deep Earth: A vision for view on CET’s performance. In the CET Annual Australian exploration geosciences”, a call for Review we commence by reiterating CET’s Vision, Australian earth scientists to cooperate in an Mission and Objectives, and then report on innovative, structured and nationally coordinated CET’s performance. The success of CET can be strategic venture that will bring competitive measured in three areas: financial performance advantage to Australian mineral exploration. and sustainability, the quality of the team, and the More information on the Exposure Draft of quality and impact of the research and training CET Searching the Deep Earth can be found is undertaking. By all of these measures, CET is on the Academy of Science website: performing very well. With success and continued www.science.org.au/policy/uncover.html/ www.cet.edu.au 3 CET NEWSLETTER ISSUE 20 JUNE 2012 continued from page 1. to-face collision with the Halmahera arc (Rohrlach & Linkages between geodynamic stress regime and Loucks, 2005). magma chemistry and gold ore productivity can be recognised most confidently in arc segments (2) Arc-arc junctions: Arc junctions are strongly containing young gold deposits in relatively well favourable sites for development of magmatic- characterised tectonic settings. Figure 1 shows the hydrothermal gold deposits. Examples in Figure distribution along the northwestern Pacific margin of 1 include the Plio-Pleistocene Kumroch high- magmatic-hydrothermal gold deposits younger than sulphidation and porphyry deposits in the Kumroch 6 Ma, containing between 10 and 600 tonnes Au in Thrust Belt at the Kurile-Aleutian arc junction; production and/or reserves, and having relatively Teine and Chitose and other high- and medium- well characterised geodynamic